Unless otherwise indicated herein, the materials described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section.
Electrical double layer capacitors (EDLCs) are commonly used to store large charge densities for high rate power extraction in place of batteries and other types of capacitors. In this technology, charge is stored at the interface of high porosity carbon particles and the electrochemical double layer of an electrolyte. This is accomplished by polarizing the capacitor in one bias direction for storage and discharging in the opposite direction for power recapture. High power extraction rates are possible using EDLCs in comparison to other capacitor types due to the accumulation of charge on the porous carbon particles. Some electrochemical capacitors operate using reduction/oxidation (redox) reactions for charge transfer, called pseudo-capacitance. EDLCs are commonly used in place of basic electrolytic capacitors and batteries because of their high energy density and high power extraction rates in technologies such as energy systems, hybrid cars and railway systems within the transportation industry. As EDLCs become more useful in commercial technology, where fast charging and high energy storage is necessary, a capacitor structure that can store a maximum amount of charge and can rapidly charge and discharge is desirable.
The present disclosure appreciates that there are several limitations with known electrochemical capacitors. The use of porous carbon particles or charcoal in a typical EDLC for storage of charge limits the maximum amount of energy density, charge storage, and power extraction.